I Love my wife, should I leave?

Me and my wife have been married for 13yrs. Have a 9yr old son. There is a 15 yr age gap between us. We love each other and have a great relationship, intimacy has fallen off though. As I’m getting older I have been struggling over the past year with the age difference. I’m now 54 and she is 39. I’m my heart I feel that in the long run she would be better off with someone closer to her age. In 16yrs I will be 70 and she will be 55. It’s not fair for her to possibly turn into a care giver to an elderly man when she is 55. I would rather let her go now and endure the pain then to take anymore of her youthful life away. I’m needing help guys.